This invention relates to an evaporative condenser which is equipped to refrigeration or air-conditioning systems using water instead of air to cool the hot refrigeration coil by transferring heat from the hot refrigerant to the cooling water in multiple cooling stages. The water absorbs heat to make water vaporize into the air in a process known as evaporation, which is a natural physical phenomenon where water absorbs heat energy to change water from the liquid phase to vapor phase, resulting in a lower temperature. The beauty of this natural phenomenon is that the evaporation is able to lower the temperature of the said vapor departure spot below the ambient temperature. The temperature decrease is small, but provides a major advantage over air cooled since air cool condenser can never get lower than the ambient temperature.
Evaporative condensers have an excellent cooling capacity, which translates into significant energy saving. For example, lowering the temperature by 13° F. of the condensing unit of a 10 SEER conventional air condition systems can reduce the power consumption by as much as 20%. This energy saving goal can be easily achieved by the systems equipped with evaporative condensers. Few will deny the superiority of evaporative condensers over the popular air cool condensers. In this case, it is our solemn duty to find out the reasons that the evaporative condensers have no place in the refrigeration and air-conditioning application. Other than the higher energy efficiency, something else must be missing. Indeed, two major drawbacks are: (1) evaporative condensers do not last too long, (2) proper maintenance of evaporative condensers is difficult.
The life of an evaporative condenser is unexpectedly short, due to the fact that the evaporative condensers have direct contact with the cooling water. For example, water is directly sprayed on the evaporative condenser by a nozzle as illustrated by U.S. Pat. No. 4,974,422, and the evaporative condenser is covered by the wet absorptive material as illustrated by U.S. Pat. No. 6,286,325. The evaporative condenser is consistently wet with water and exposed to air (oxygen) which creates a corrosive environment for metal. Under this condition, the refrigeration tubing made of copper and the evaporative condensers made of other metals will rust. The rust will be able to totally breakdown the evaporative condenser in about two years. The energy saved does not pay off the cost of a new unit in two years.
The other drawback of evaporative condensers is that the quickly depositing scale decreases the heat transfer rate. Un-attendance to the scale deposit problem could lead to system failure. Yet, there is little or no help from the current design to solve the scale deposit problem. U.S. Pat. No. 4,974,422 states: “The spray of a relatively large volume of cooling water washes away scale which would build up due to evaporation . . . . ” This method does not work since scale is the byproduct of evaporation. More water may make more scale counterproductively. Removing scale out from a condensing coil is a high level difficulty job, due to the fact that the scale deposit into a coil is not in an area easily accessible. Also not much force or chemical can be applied to a refrigeration coil to remove scale. It is very hopeless to clean scale out from a condenser. The best remedy to this problem is not to allow scale deposit into the refrigeration coil.
The present invention does not allow the cooling water to directly contact the refrigeration coils, so no scale can be deposited into the condensing coils. Evaporation takes place in the water pans with non-stick coating. Scale deposited in the water pans is loose and can be easily removed anytime. Also, the cooling method of the present invention can significantly prolong the life of an evaporative condenser, which can last as long as the other conventional air cool condensers.